[Sophia7X]

http://portal.acs.org/portal/PublicWebSite/education/students/highschool/olympiad/pastexams/CNBP_021762

the question I am having problems with is #5.

The answer is supposed to be B but I can only get A. I used the highest point on the graph (probably around 70 mL) but it didn't work.

[Borek]

Approximate both left and right parts with a straight lines. Where do they cross?

[Sophia7X]

Approximate both left and right parts with a straight lines. Where do they cross?

oh, thanks! I didn't think to do that; I just drew a curve through the dots. 75 works.


On the same test, #35... why isn't this graph a diprotic acid?

[Dan]

On the same test, #35... why isn't this graph a diprotic acid?

For a diprotic acid, if the first equivalence point is reached after adding x mol of NaOH, how much more NaOH do you need to add to reach the second equivalence point?

[Sophia7X]

So it's not diprotic because the second equivalence point would require 2x?

[Borek]

Yes.